Peptide concentration gradients and aligned microfiber topography synergize to speed and direct Schwann cell migration

Conjugating precise concentrations of bioactive peptides on aligned topographies holds a promising application in directionally guiding Schwann cell migration, a significant step in peripheral nerve regeneration. To harness this behavior, we have developed aligned fiber scaffolds functionalized with variable concentration gradients of YIGSR, a laminin-derived peptide known to promote Schwann cell motility. Using thiol-ene click chemistries, we generated uniform and gradient patterns of YIGSR on the aligned fibers with spatial control over tethered peptide concentration during fabrication, yielding two uniform concentration scaffolds of 100 pmol/cm² and 420 pmol/cm² YIGSR, and three gradient profiles of slopes 7 pmol·(cm²·mm)⁻¹, 15 pmol·(cm²·mm)⁻¹, and 60 pmol·(cm²·mm)⁻¹. Schwann cell migration on scaffolds revealed that uniform YIGSR functionalization enhanced migration in a sex-specific and concentration-dependent manner. Female Schwann cells responded with greater migration on 100 pmol/cm² uniform YIGSR-functionalized fibers while male Schwann cell migration was enhanced on fibers with both 100 and 420 pmol/cm² compared to non-functionalized fibers. However, guidance of cell migration can not be achieved with increasing cell speed alone. Therefore, gradients were fabricated directly on the fiber scaffolds and quantified. While shallow YIGSR gradients (7 and 15 pmol·(cm²·mm)⁻¹) did not consistently bias Schwann cell directionality in the direction of the gradient, 60 pmol·(cm²·mm)⁻¹ gradient profiles induced a haptotactic response, measured by directional velocity and haptotactic index, with both sexes migrating toward regions of higher peptide concentration. Thus, along with contact guidance effects provided by aligned fibers, precisely-defined peptide-functionalized gradients can be used to further bias Schwann cell migration for nerve regenerative applications. STATEMENT OF SIGNIFICANCE: Peripheral nerve injuries often result in incomplete recovery, partly because cells crucial for repair cannot efficiently move into injury sites. While researchers have developed aligned fibers that act as a pathway for the cells into the injury site, cells are free to move in any direction along the path, reducing their ability to support repair. This study demonstrates that by combining aligned fibers with bound chemical gradients to act as guard rails, cells move preferentially in one direction along the pathway. By precisely controlling both the fibers' physical alignment and chemical gradients, we achieved unidirectional cell migration. This dual-cue approach represents a significant advancement in biomaterial design for nerve repair, offering a promising strategy to enhance regeneration across nerve defects.